Ultracoherent self-assembled diamond nanomechanics reveals superfluid dynamics

TL;DR

This paper reports the creation of ultra-coherent diamond nanomechanical resonators with record-high quality factors, revealing new insights into dissipation mechanisms including surface superfluid helium films, advancing quantum and precision measurement technologies.

Contribution

The authors develop a strain-engineered diamond nanomechanical platform with tensile stress exceeding 1 GPa, achieving unprecedented coherence and enabling the study of dissipation channels in diamond.

Findings

Achieved quality factors beyond 10 billion at cryogenic temperatures.

Identified three two-level-system dissipation channels and one surface superfluid helium film channel.

Demonstrated the potential for new physics in hybrid quantum systems and precision metrology.

Abstract

From gravitational-wave detection, protein force microscopy, to exploration of quantum-classical boundaries, many anticipated discoveries in fundamental science require improving measurement sensitivity limits. Through the fluctuation-dissipation theorem, mechanical dissipation sets the acoustic noise for this limit. Yet, even in high-purity crystals, the microscopic mechanisms responsible for the acoustic loss remain poorly understood. Tension-induced dissipation dilution offers a route to ultralow acoustic loss, but is challenging to implement in crystalline materials including single-crystal diamond. Here we realize a strain-engineered diamond nanomechanical platform using a liquid-assisted van der Waals self-assembly process that harnesses intrinsic surface forces to apply tensile stress exceeding 1 GPa. At cryogenic temperatures these resonators achieve quality factors beyond 10 billion (intrinsic material quality factors beyond 100 million). This exceptional coherence turns them into a sensitive probe for residual dissipation, elucidating three distinct two-level-system channels and one topological dissipation channel from a surface superfluid helium film. Our work shows how advancing mechanical coherence opens access to new regimes of physics in hybrid quantum systems, precision metrology, and condensed-matter physics.